Short Range Forecast - Regional system and others Yuejian Zhu Ensemble Team Leader EMC/NCEP/NWS/NOAA Acknowledgements: EMC ensemble team members Presents

Short Range Forecast

- Regional system and others

Yuejian Zhu

Ensemble Team Leader

EMC/NCEP/NWS/NOAA

Acknowledgements: EMC ensemble team members

Presents for NWP Forecast Training Class

March 31, 2015, Fuzhou, Fujian, China

Short Range Forecast• What is important?

– Extreme weather– High impact weather– Daily forecast

• WPC – Weather Prediction Center– Daily briefing – map discussion– Subjective use of ensemble– Objective use of ensemble– Coordinate to WFO

• SPC – Storm Prediction Center– Sever weather – Coordinate to WFO

• AWC – Aviation Weather Center– Current and nowcasting– Connected to FAA

• Testbed for each service center– NOAA Hydrometeorological Testbed at WPC– NOAA Hazardous Weather Testbed at SPC– NOAA Aviation Weather Testbed at AWC

• Example – joint probability• Important forecast products

Introduction • Extreme weather events

– Unusual, Unexpected, rare weather events– Cost: loss of lives, properties, equipment and etc.– Forecast: may be difficulty, may be not– Alarms to users (such as Watch, Warning and etc…)– Early decision and early protection– Widely social impacts– Always use updated forecast information

• Deterministic and probabilistic forecast– Easy missing extreme event from deterministic forecast– Using ensemble based forecast– Forecast in terms of probability or possibility – Wide coverage of the weather events from probabilistic sense,

include extreme weather events.– Consider multi-variables (temperature, precipitation, wind and etc…)

Definition of Extreme Events • Climatological extremes

– Based on climatological distributions.– The tails (5% or less) of climatological distribution.– Considering a particular meteorological variable.– Considering a specific time and place.

• Forecast extremes– similar to climatological extremes– Different range and values of distribution.– Narrow band than climatology.– Conditional climatological sense.

• User specific extremes– User defined extreme (not climatology, not forecasting).– For particular user, in particular area and time period– Sensitivity to particular area and in time period– Sensitivity to particular meteorological element.– The combination of the temporal/spatial.

Nature of Extreme Events • Physical system.

– The same for extreme and non-extreme events.– Different from phase space of system.– Near the edge of the distribution.– Small scale system in generally.

• Nonlinear process.– Play a crucial role to define the “edge”.– Creating additional uncertainty.– Model’s limitation to predict extreme by nonlinear process.

• Combination of many factors:– Snow covers, cloud covers.– Minimum temperature, and maximum temperature.– Combined high temperature and high humidity – heat index– Wind speed, combined cold temperature and wind sheer.– Precipitation amount and concentration.– Time, location and etc…








WPC Daily DiscussionsExplanation of Abbreviations and Acronyms Used in These Products

Short Range Public Forecast Discussion (PMDSPD) Extended Forecast Discussion (PREEPD or PMDEPD. See note below)* Quantitative Precipitation Forecast (QPF) Discussion (QPFPFD) Excessive Rainfall Discussion (QPFERD) Heavy Snow Discussion (QPFHSD) Model Diagnostic Discussion (PMDHMD) National High and Low Temperature NAM Air Quality Diagnostic Discussion Hawaiian Message (PMDHI) Alaskan Extended Forecast Discussion South American Synopsis (PMDSA) South American Model Discussion (PMDSA) Caribbean Narrative (PMDCA) Storm Summaries Latest Storm Summary (updated 0244Z 01/18/2013) SCCNS1 SCCNS2 SCCNS3 SCCNS4 SCCNS5 Tropical Public Advisories - Atlantic Latest Tropical Advisory (updated 1500Z 10/31/2012) TCPAT1 TCPAT2 TCPAT3 TCPAT4 TCPAT5 Tropical Public Advisories - Pacific Latest Tropical Advisory (updated 1500Z 09/06/2007) TCPEP1 TCPEP2 TCPEP3 TCPEP4 TCPEP5

HPC daily briefing is 30 minutes from 11:00-11:30am (weekday only)

WPC 3-day forecast

WPC - Subjective Use of Ensembles (1)

• Assess predictability• Establish forecaster confidence• Identify outliers and clusters• Identify preferred solutions

Spaghetti Low ClustersQPF isohyets

Mean/Spread

Courtesy of Dan Peterson


Identify preferred solutions

Used as inputs to model blends (weights) selected by forecasters for first-guess forecast

Courtesy of Dan Peterson


Uncertainty information communicated via forecasts, discussions and user-interactions

WPC - Objective Use of Ensembles (4)

Combine manual deterministic forecast with ensemble distribution and spread to generate probabilities

Deterministic Snow Deterministic QPF

Role of the Forecaster

13

WPC - Objective Use of Ensembles (5)

Probability > 4” Snow Probability > 0.50” QPF

14

Role of the Forecaster

Combine manual deterministic forecast with ensemble distribution and spread to generate probabilities








Example of SPC real time warning and short-term forecast

This map displays active watch, warnings, advisories and short term forecasts in the lower 48 US states. This page will automatically refresh every five minutes.

SPC fire weather outlook (day 3-8)Scalloped line represents a critical threat of dry thunderstorms with dry fuels within 12 miles of a point. The delineation is equivalent to a 40% probability of occurrence.Solid line represents a critical threat of strong winds, low relative humidities, and warm temperatures concurrent for at least 3 hours with dry fuels within 12 miles of a point. The delineation is equivalent to a 70% probability of occurrence.

Day-4 forecastGeneral FW outlook







• Example – joint probability

The front page of NCEP Aviation Weather Center

AFCfrom METARs

LIFR IFR MVFR

(icg) PIREPs (turb)LGT MOD SEV LGT MOD SEV

Visibility/fog, turbulence, icing, convection, winds/temperature and etc…

http://aviationweather.gov/








NOAA Hydrometeorological Test Bed at WPC

• The Hydrometeorological Testbed (HMT) at the Weather Prediction

Center (HPC) was established by the National Oceanic and

Atmospheric Administration (NOAA) in order to accelerate the

assessment and implementation of new technology, research results,

and other scientific advancements from the research and development

communities to enhance HPC products and services. The HMT-HPC is

designed to enhance and extend forecast skill for high-impact weather,

especially precipitation, by facilitating interactions among researchers,

operational forecasters, and users. Ultimately, project proposals

related to this mission will be solicited from both the meteorological and

hydrological communities.

• If you are a researcher and would like to work with the HMT-HPC,

please read about our research to operations (R2O) goals and

objectives.

WSR - Winter Storm Reconnaissance• Improving high impact weather forecasts by adaptive observing, data

processing • Using NCEP, CMC and ECMWF ensemble forecasts

– 4 cycles per day for NCEP ensembles– 2 cycles per day for CMC and ECMWF ensembles

• NCEP operational since 2007– NCO and EMC

• Winter period:– December – March every year

• Maintenance– Codes/scripts will be tested for each system upgrade– Codes/scripts will be tested before every winter season started

• Evaluations– Through THORPEX funding (out now?)– Limited evaluations – collaborated with ESRL and ECMWF to target observation

evaluation (Fanglin Yang)– Reference: Tom Hamill is leading this manuscript

CSTAR Program

• CSTAR - Collaborative Science, Technology, and Applied Research Program

• Collaborate with SUNYSB, EMC, WPC, OPC of NCEP and ESRL

• Predictability of high impact weather during the cool season over the eastern U.S: from model assessment to the role of the forecaster

• Produce daily ensemble sensitivity analysis maps based on– NCEP GEFS– CMC GEFS– ECMWF GEFS (passwd protected)

• A set of variables – MSLP and 500hPa height– CSTAR web-site: http://dendrite.somas.stonybrook.edu/CSTAR/– EMC web-site: http://www.emc.ncep.noaa.gov/gmb/yluo/CSTAR/

http://dendrite.somas.stonybrook.edu/CSTAR/

http://dendrite.somas.stonybrook.edu/CSTAR/

http://www.emc.ncep.noaa.gov/gmb/yluo/CSTAR/



24

Daily maps to support CSTAR program for winter season

NOAA Hazardous Weather Testbed (SPC)Bringing Severe Storm Research into Operations

NOAA's Hazardous Weather Testbed (HWT) is a facility jointly managed by NSSL, the Storm Prediction Center (SPC), and the NWS Oklahoma City/Norman Weather Forecast Office (OUN) within the National Weather Center building on the University of Oklahoma South Research Campus. The HWT is designed to accelerate the transition of promising new meteorological insights and technologies into advances in forecasting and warning for hazardous mesoscale weather events throughout the United States. The HWT facilities include a combined forecast and research area situated between the operations rooms of the SPC and OUN, and a nearby development laboratory. The facilities support enhanced collaboration between research scientists and operational weather forecasters on specific topics that are of mutual interest.

The HWT organizational structure is composed of two primary overlapping program areas, the Experimental Forecast Program and the Experimental Warning Program. The EFP focuses on application of cutting edge numerical weather prediction models to improve severe weather forecasts. The EWP tests research concepts and technology specifically aimed at short-fused warnings of severe convective weather.

A key NWS strategic goal is to extend warning lead times under the concept of "warn-on-Forecast" through the development and application of convection-allowing numerical models to extend short-term predictability of hazardous convective weather. This provides a natural overlap between the EFP and EWP activities. As the distinction between warnings and short-term forecasts of convective weather gradually diminishes, the degree of overlap is expected to increase. Both programs reside beneath the overarching HWT organization with a focus on national hazardous weather needs.

The cornerstone of the testbed is the annual NOAA HWT Spring Experiment that attracts about 100 researchers and forecasters to Norman each year. The premise of each Spring Experiment and related activities is to provide forecasters with a first-hand look at the latest research concepts and products, while immersing research scientists in the challenges, needs, and constraints of front-line forecasters. In practice, this program gives forecasters direct access to the latest research developments while imparting scientists with the knowledge to formulate research strategies that will have practical benefits. The end result is not only better severe-weather forecasts, but important contributions to the scientific literature as well.

NOAA's Aviation Weather Testbed (AWC)

• Project – The Aviation Weather Testbed provides a means of testing new science

and technology for the purpose of eventually producing better aviation weather products and services. The execution of the Testbed is accomplished via close collaboration between the AWC and its many partners.

• Purpose – Provide a path to operational use for experimental products and

services– Invite the participation of third parties– Provide a test environment for the purpose of refining and optimizing

experimental forecast tools– Verify the scientific validity of experimental products– Educate forecasters about experimental tools and the latest research

related to aviation weather forecasting– Educate researchers about operational forecast needs and constraints



• HPC – Weather Prediction Center– Daily briefing – map discussion– Subjective use of ensemble– Objective use of ensemble– Coordinate to WFO





SREF Probability of STP Ingredients: Time Trends

48 hr SREF Forecast Valid 21 UTC 7 April 2006

Prob (MLCAPE > 1000 Jkg-1)

X

Prob (6 km Shear > 40 kt)

X

Prob (0-1 km SRH > 100 m2s-2)

X

Prob (MLLCL < 1000 m)

X

Prob (3h conv. Pcpn > 0.01 in)

Shaded Area Prob > 5%

Max 40%

Courtesy of David Bright




X


X

Prob (0-1 km SRH > 100 m2s-2)

X


X



Max 50%




X


X

Prob (0-1 km SRH > 100 m2s-2)

X


X



Max 50%




X


X

Prob (0-1 km SRH > 100 m2s-2)

X


X



Max 50%

Severe Event of April 7, 2006• SREF environmental guidance increased forecaster

confidence leading to a “High Risk” Day 2 outlook• This was the first Day 2 High Risk ever issued by SPC • Impact: More than 800 total severe reports

– 3 killer tornadoes and 10 deaths








Two Important Diagnostic Products

• CAPE – Convective Available Potential Energy– is the amount of energy a parcel of air would have if

lifted a certain distance vertically through the atmosphere. CAPE is effectively the positive buoyancy of an air parcel and is an indicator of atmospheric instability, which makes it very valuable in predicting severe weather

• CIN – Convective Inhibition– is a numerical measure in meteorology that indicates

the amount of energy that will prevent an air parcel from rising from the surface to the level of free convection.

Figure: Schematic diagram showing an air parcel path when raised along B-C-E compared to the surrounding air mass Temperature (T) and humidity (Tw)

LSC – Level of Start Convection

LCL – Lifted Condensation Level

LFC – Level of Free Convection

CIN – Convective InstabilityCAPE – Convective

Available Potential EnergyEL – Equilibrium Level

W – Vertical MotionDP(w) – SAS trigger

function (delta pressure)R(N) – Random function (small delta pressure)

PLSC-PLFC <= DP(w) Convection is triggered,

PLSC-PLFC > DP(w) No sub-grid convection

W

DP(W)

R(N)

LSC

CAPE• It is a form of fluid instability found in thermally stratified

atmospheres in which a colder fluid overlies a warmer one. As explained below, when an air mass is unstable, the element of the air mass that is displaced upwards is accelerated by the pressure differential between the displaced air and the ambient air at the (higher) altitude to which it was displaced. This usually creates vertically developed clouds from convection, due to the rising motion, which can eventually lead to thunderstorms. It could also be created by other phenomena, such as a cold front. Even if the air is cooler on the surface, there is still warmer air in the mid-levels, that can rise into the upper-levels. However, if there is not enough water vapor present, there is no ability for condensation, thus storms, clouds, and rain will not form.

CAPE (continue)

• When a parcel is unstable, it will continue to move vertically, in either direction, dependent on whether it receives upward or downward forcing, until it reaches a stable layer (though momentum, gravity, and other forcing may cause the parcel to continue). There are multiple types of CAPE, downdraft CAPE (DCAPE), estimates the potential strength of rain and evaporatively cooled downdrafts. Other types of CAPE may depend on the depth being considered. Other examples are surface based CAPE (SBCAPE), mixed layer or mean layer CAPE (MLCAPE), most unstable or maximum usable CAPE (MUCAPE), and normalized CAPE (NCAPE).

• NCEP produces two CAPEs– CAPEsfc and CAPE180_0mb

CIN• CIN is the amount of energy required to overcome the negatively buoyant energy

the environment exerts on an air parcel. In most cases, when CIN exists, it covers a layer from the ground to the level of free convection (LFC). The negatively buoyant energy exerted on an air parcel is a result of the air parcel being cooler (denser) than the air which surrounds it, which causes the air parcel to accelerate downward. The layer of air dominated by CIN is warmer and more stable than the layers above or below it.

• The situation in which convective inhibition is measured is when layers of warmer air are above a particular region of air. The effect of having warm air above a cooler air parcel is to prevent the cooler air parcel from rising into the atmosphere. This creates a stable region of air. Convective inhibition indicates the amount of energy that will be required to force the cooler packet of air to rise. This energy comes from fronts, heating, moistening, or mesoscale convergence boundaries such as outflow and sea breeze boundaries, or orographic lift.

• Typically, an area with a high convection inhibition number is considered stable and has very little likelihood of developing a thunderstorm. Conceptually, it is the opposite of CAPE.

The “Best CAPE/CIN” - Xiakun Zhang

• Use virtual temperature correction– Tv instead of T or potential temperature– Many numerical product has adopt this method

• Average properties– Besides selecting the surface, various schemes choose a parcel with the average

properties within some layer (Doswell et al., 1993).

• Most unstable parcel– Doswell et al. (1994) proposed to pick the most unstable parcel in the lowest layers.

• NCEP GFS/GEFS products– The variable “CAPE180_0mb” take the six 30-mb averaged layers closest to the

ground and lift the most unstable one.– This is a combination of “ML-CAPE” and “MU-CAPE”.

• For CIN, there is a similar analysis.• Results:

– When CAPE is large, CAPE180_0mb is less than CAPEsfc; – When CAPE is small, CAPE180_0mb is greater than CAPEsfc.

Documents

Short Range Forecast - Regional system and others Yuejian Zhu Ensemble Team Leader EMC/NCEP/NWS/NOAA Acknowledgements: EMC ensemble team members Presents